Method of preparing thioethers



United States Patent 3,206,467 METHOD OF PREPARING THIOETHERS WalterReifschneider, Midland, Mich, assignor to The Dow Chemical Company,Midland, Mich, a corporation of Delaware No Drawing. Filed June 27,1962, Ser. No. 265,516 3 Claims. (Cl. 260302) The present invention isdirected to a novel method for the preparation of thioethers, and tocertain thioethers prepared thereby.

According to the present invention I have discovered a novel generalmethod for the preparation of thioethers which permits the synthesis ofthioethers of very wide variety including many thioethers hithertounknown and impossible to synthesize. Among the kinds of thioethers tobe prepared in the new method are polythioethers, and polyetherscomprising a plurality of recurring chalkogen linkages whereof certaindesired members are sulfur; and substituted derivatives of suchcompounds.

The novel method of the present invention may be representedschematically as follows:

wherein R and R are organic groups, X is a halogen, Cu+ is a source ofcuprous ions and N+ represents a nitrogenous base. Thus, the presentgeneral method for the synthesis of thioethers may be described as amethod which comprises causing a reaction between a mercaptan and anorganic halide in the presence of both a nitrogenous base and a sourceof cuprous ions. It will at once be apparent to skilled chemists that bythe choice of mercapstans containing a plurality of sulfhydryl groupsand the subsequent employment of poly-halogenated compounds, the methodof the present invention permits the synthesis of polymers whereinrecurring organic groups such as aliphatic or aromatic groups are bondedtogether by intervening divalent sulfur atoms. Similar polymers areprepared from the employment of mercaptans containing also halogens,whereof the halogen provides a reactive site at which the :sulfhydrylgroup can, by reaction, set up a thioether linkage. Polymers ofrelatively low molecular Weight are produced in good yield in this way.

Various novel thioethers including polymeric thioethers newly preparedby the present novel method are also comprehended within the presentinvention.

It is known to react alkali metal mercaptides of a very limited rangewith lower alkyl or, rarely, aryl halides in inert reaction medium. Thismethod has been limited to aryl halides in which the halogen substituenthas been activated by the presence on the aryl nucleus ofelectronwithdrawing groups, such as nitro groups, and they in ortho orpara positions to the halogen. By this method it is possible to producea few thioethers. However, prior to the present method it has beenimpossible to prepare such relatively simple thioether compounds as32%,467 Patented Sept. 14, 1965 in one step and in good yield. Now Ihave discovered that almost any mercaptan, which may be an alkyl,cycloalkyl, heterocyclic or aryl mercaptan, and almost any organichalide, which may be an aromatic, heterocyclic, alicyclic or aliphatichalide, either starting material being of any molecular weight, may becontacted together in the presence of a nitrogenous base and a cuprouscompound, the resulting reaction mixture heated to a reactiontemperature whereupon there is prepared, in a single process, athioether compound comprising organic moieties derived from themercaptan and from the organic halide. The only limit upon the startingmaterials is that they be relatively stable under reaction conditionsand that they be relatively not seriously hindered by stericrelationships of substituents. The method does not produce desiredcompounds efficiently when starting material or product is, or becomes,unstable before reacting. The reaction releases the elements of hydrogenhalide.

In one embodiment of my invention, copper in any convenient form isemployed instead of, or as a source of cuprous ions. In such embodiment,the copper source, which may be metallic copper, copper oxide orhydroxide, and the like, reacts in some way to become an effectivecuprous catalytic substance. Thus while I believe cuprous ions to be,part of the active catalytic agent in some kind of cooperation with thenitrogenous base, the copper may be added to the reaction mixture in anyconvenient form which is capable of reacting, in such mixture, to obtaina cuprous compound. When desired, the copper may be added as cuprouscompound, for example, cuprous chloride, in the first instance.

In carrying out the preparation of the thioethers according to the novelmethod of the present invention, an appropriate mercaptan, coppercatalytic substance or precursor thereof, a liquid reaction medium, anda nitrogenous base are combined to obtain a reaction mixture. The metalsalt of a mercaptan may be employed when desired, instead of the freemercaptan. Such salt may offer the advantage of being easier to workwith. The reaction medium may be an inert liquid reaction medium such asbenzene, toluene, a lower alkanol or a lower alkyl ether, or the like;when an inert liquid reaction medium is employed the necessarynitrogenous base is added thereto. Such nitrogenous base may be, forexample, a primary, secondary, or tertiary lower alkyl amine, or a loweralkanol amine, or the amine requirement may be met by the presence, assubstituent upon one or more of the reactants to be employed, of anamine group. If desired, both nitrogenous catalyst and reaction mediumrequirements may be met by employment of an amine-type liquid reactionmedium such as pyridine, lutidine, picoline, aniline, dimethylaniline,xylidine, N,N- dialkylxylidine or an aromatic or aliphatic amine chosenas being liquid under the reaction conditions. Such amine-type liquidmay be employed alone, or may be employed as part of a liquid medium ofwhich other parts are inert liquids. Inanother manner of practicing thepresent invention, the catalytic amine compound requirements may be metby the employment, in the reaction mixture, of ammonia, or source ofammonia or of amsponsor 0.3 monium ion, as supplied by the presence ofan ammonium compound.

Thus, copper compounds which may be used and are effective as sources ofcuprous ions or precursors thereof in practicing the present invention,include copper acetate, basic copper acetate, copper benzoate, coppermetaborate, cuprous bromide, cupric bromide, cupric butyrate, cuprouscarbonate, basic cuprous carbonate, cupric chloride, cuprous chloride,cupric ethylacetoacetate, cupric fluoride, cupric formate, cuprousformate, cuprous hydroxide, cupric hydroxide, cuprous iodide, cupriclactate,

' cupric laurate, cupric oleate, cupric oxalate, cuprous suboxide,cupric palmitate, cupric orthophosphate, cupric salicylate, cupricstearate, cuprous sulfate, cupric sulfate, cuprous sulfite, cuprictartrate, diammine copper acetate, tetrammine copper sulfate. Coppercompound-s which act as oxidizing agents are usually first reduced byoxidation of mercaptan and would thus be moderately wasteful ofmercaptan, but are nonetheless successful when this is allowed for. Suchsubstances include copper bromate, copper chlorate, cupric dichromate,cupric iodate, cupric nitrate, basic cupric nitrate, cupric oxychloride,and the like. In these and any of a great many similar and relatedforms, copper is successfully employed, in the present reaction, eitheras a direct source of cuprous ions or as a source of copper which, byreacting in the present mixture, gives rise to cuprous ions. Cupriccompounds are readily converted to cuprous compounds when employing thestated conditions, although their use may be wasteful of mercaptanreactant.

At least in laboratory procedures, it is convenient to employ a liquidcompound of the pyridine type such as the picolines, lutidines,collidines, and quinolines as solvents. The nitrogenous base may be asolid at room temperature and, in use, may be either dissolved ormelted.

The reaction employs as starting materials organic halides which, in thepresence of an excess of harsh basic substances such as alkali metalhydroxides, tend to decompose forming alkali metal halides and variousorganic decomposition products. Thus if alkali metal compound is used aspart or all of the hydrogen halide inactivating substances, thematerials should be used in amounts not much greater than an amountequimolecular with employed mercaptan.

When the reaction employing a mercaptan goes forward with formation ofhydrogen halide or at least the elements of hydrogen halide, suchhydrogen halide or the elements thereof tend to react with halideaccepting substance which may include the nitrogenous basic catalyticsubstance Subsequent to such reaction, the resulting nitrogenousmaterial is no longer basic and its catalytic effectiveness is in someway lost. Therefore, it is essential and critical that the nitrogenousbasic catalytic material (which may be a mixture of various nitrogenousbasic substances, chosen for such considerations as cost, boilingtemperature, and the like) be supplied in a total amount at leastslightly greater than that equirnolecular with hydrogen halide to beevolved in the course of the reaction, or than that not otherwiseinactivated.

In a minor and obvious variation of the present method the mercaptan mayfirst be reacted (in the reaction mixture wherein other steps of thepresent method are subsequently to be employed, if desired) with a basicalkali metal compound to prepare the alkali metal mercaptide; thissubstance is subsequently employed in the manner indicated for thegeneral method. When this method is used, alkali metal halide is formedand, while it has no tendency to consume basic nitrogenous catalyticsubstance, may require filtration, aqueous extraction, or the like toremove salt by-product from the resulting product mixture.

Although the nitrogenous basic substance is consumed in certainindicated procedures for carrying out the present method, it may, in theinstance of many such substances be regenerated or reconstitute-d intoits origin- .ployed, the reaction goes forward at a good rate.

al, catalytically useful form by means no more difficult than steamdistillation in the presence of such cheap basic material as slakedlime, or limestone.

When liquid nitrogenous base is employed as liquid reaction medium theemployed amount is usually entirely suflicient, otherwise, an inertliquid reaction medium may be employed together with suflicientnitrogeneous base for catalysis and hydrogen halide acceptance, in themanner described.

It is thus apparent that the nitrogeneous base compounds to be employedas a component in the catalyst system of the method of the presentinvention include monomethylamine, dimethylamine, trimethylamine;monoethylamine, diethylamine, triethylamine; mono-npropylamine,di-n-propylamine, tri-n-propylamine. Those which are gases or volatileliquids are employed under pressure or in solvent solution or arecontinuously supplied Other useful compounds include monoisopropylamine,diisopropylarnine, triisopropylamine; mono n butylamine,di-n-butylamine, tri-n-butylamine; N,N-dimethyl- N-tertiarybutylamine;cyclohexylamine; the various aliphatic amines of low to intermediatemolecular weight, characteristically of mixed isomeric structure,available commercially under the trademark Armeen; nitrogenous compoundsand nitrogeneous bases including aliphatic and aromatic heterocyclicnitrogen compounds, and substituted compounds containing, for example,one or more aromatic groups such as aniline, N-methylaniline, andsimilar basic derivatives of aniline. Also, the amino alcohols such asthe alkanolamines are effective nitrogenous base catalytic materials.For example, monoethanolamine, diethanolamine, triethanolamine, thepropanolamines and isopropanolamines, and other alkanolamines which haveuseful physical properties are satisfactorily employed.

The employed amounts of either the nitrogenous base component or thecuprous component of the composite catalyst to be employed in thepresent invention is not critical so long as both in fact, are andremain present. In general, when amounts less than 1 mole percent ofcatalyst are employed, the reaction goes forward more slowly than whenmoderately larger amounts are employed. On the other hand, when as muchas 5 molar percent is em- The employment of a larger amount of either orpreferably both catalyst components is usually attended by increasingbenefits in proportion to the amount of catalyst employed, up to anamount about equimolecular with limiting starting reactant. As has beennoted, due allowance is to be made for the consumption of nitrogenousbase by reaction with hydrogen halide.

The reaction of the present method is somewhat temperature dependent. Ata temperature lower than a preferred reaction temperature, the reactionof the mercaptan compound (free mercaptan or salt such as alkali metalsalt), and the organic halide usually goes forward, but at a rate soslow as to be relatively inefiicient. When the reaction mixture isheated to a reaction temperature, the reaction takes place promptly andgoes to completion without undue delay. A preferred reaction temperatureis a temperature in the range of from about to about 250 C. In general,the lowest efficient reaction temperature or the reflux temperature ofsolvent, is to be preferred.

Although, as has been stated, successful procedures in which to preparethe present products are somewhat temperature dependent, it is notnecessary to know, in advance, the precise temperature at which areaction will take place. Ordinary heating means of laboratory orindustrial type are adequate and any of a Wide range of liquid reactionmedia may be employed. The conditions are met for the preparation ofaromatic thioether products of an extremely wide variety by employmentof quinoline or a substituted quinoline compound which boils stably andhas a relatively high boiling temperature, as reaction medium. For thepreparation of almost all aliphatic thiois v J ether compounds,2,4-lutidine is a satisfactory nitrogenous base and reaction medium.However, when it is desired to do so, other nitrogenous base compoundsof the sort previously described may be employed with good results.

Under ordinary conditions of carrying out the present reaction, some ofthe substances employed, or present as transitory intermediates, may berelatively susceptible of undesired oxidation. This oxidation may beprevented by the provision of an inert atmosphere which may be a movingcurrent or an unmoving atmosphere of an inert gas such as nitrogen,helium, vapor of reaction medium or of nitrogenous base substance or thelike. While such provision will commonly increase the efficiency of themethod, good results are had without any control of the atmosphereadjacent the reaction.

When it is desired to carry out the preparation of a thioether accordingto the novel method, a reaction mixture is prepared, comprising organichalide, mercaptan, nitrogenous base, and source of cuprous ions. Thecomponents may be combined in any order. The addition of organic halideto the said mixture may be carried out in the initial preparation of areaction mixture. Alternatively, the organic halide may be added at anysubsequent time, such as at the time that the reaction mixture, or amixture of some of the components thereof, has been heated to a reactiontemperature, or at other times.

When carrying out a reaction according to the present method between, onthe one hand, a polyhalo compound and on the other hand a polymercaptocompound, various courses of reaction are possible. When the employedgroups have spatial relationships which permit of multiple reactiongiving rise to ring closure, and when it is desired to prepare theproduct resulting from such polythioether ring closure, the polyhalo andpolymercapto compounds are reacted together according to the. presentmethod using a relatively large amount of solvent liquid whereby theconcentration of the reacting substances is low. Low to medium reactiontemperautres are indicated also. When between the same reactingsubstances it is desired to cause the reaction whereby to prepare arelatively linear polythioether polymer, then the reaction isadvantageously carried out at substantially higher temperatures, such asthose achieved under superatmospheric pressure, with the reactants inrelatively high concentration. The same considerations ap- "ply whenemploying a halogenated mercaptan such as to prepare, variously, linearpolymers or low polymers with ring closure.

When it is desired to carry out a reaction-between a polyhalo compoundon one hand and on the other hand a polymercapto compound whereby onlyone mercapto group reacts with only one halogenated site giving rise toa thioether compound upon which there remain unreacted halogen andunreacted mercapto groups, the reactants are employed together inapproximately stoichiometric amounts, the reaction conditions, notablyduration of the reaction and reaction temperature, are maintained atvalues near to the lower values advantageously employed in the presentmethod. In this situation, the resulting reaction mixture usuallycontains all possible products of reaction from which the desiredproduct is readily separated as by recrystallization, vacuumdistillation and the like.

Although the present method depends upon the reaction of an oragnichalide and a mercaptan, it is possible and convenient so to carry outthe reaction as to leave unreacted halogen of desired identity in anyposition upon the resulting thioether compound. Thus, for example, whenit is desired to prepare a thioether of which one representative moietyor group is a cyclic group upon which cyclic group it is desired that,for example, bromine appear as a substituent, the desired compound isprepared by causing a reaction according to the present method between amercaptan and a dibromo compound'of which one bromine is in the positionwhereupon bromine is to appear in the resulting product. The mercaptanis employed in a stoichiometric amount. As the reaction goes forward,all the various possible reaction products are prepared and at firstexist together in the resulting reaction mixture. Thereafter, the saidmixture is resolved into its various components in such known methods asdistillation, recrystallization from solvent, and the like.

When it is desired, according to the method of the present invention, toprepare a thioether compound upon which, as substituent, there appearsan unreacted halogen of the sort adapted to be employed in the reactionof the present method, advantage may be taken of the fact thatreactivities of halogens in the method of the present invention varyapproximately directly as molecular weight. Thus, for example, when itis desired to prepare a thioether in the manner of the present inventionupon one or more moieties or groups of which it is desired to have, forexample, bromine, it is convenient to begin with a starting halo-oragniccompound upon which, for reaction in the present process, iodine appearsas reactive halogen substituent and bromine appears in a positionrelative to the position of the iodine in which it is desired that thebromine appear relative to the position of the thioether linkagev in thecompleted compound. In this situation, when employing stoichiometricamounts of the reacting substances, the reaction of the presentinvention will almost completely preferentially go forward with thedisplacement of iodine leaving the brominated site almost completelyunattacked.

Similarly, when it is desired that chlorine appear on the thioetherprepared in the manner of the present invention, a chlorobrominatedstarting haloorganic compound may be employed and the brominated sitewill participate in the reaction of the present invention to the almostcomplete exclusion of the chlorinated site when equimolecular amounts ofthe reactants are employed.

Fluorine is both more expensive and more diflicult to cause toparticipate in the reaction of the. novel method; thus the use ofstarting haloorganic compounds whereof the halogen X is fluorine is notusually preferred. However, fluoroorganic compounds do take part in thereaction of the present method and may be employed if desired.

In one embodiment of the novel method of preparing the thioether, which,by reason of its economy and simplicity is a preferred method, themercaptan, organic halide, nitrogenous base, and cuprous material suchas cuprous oxide are combined in the initial reaction mixture, thecuprous material being employed in a catalytic amount, such as from 1 to125.0 mole percent by weight of employed sulfhydryl sulfur.Alternatively, the catalytic amount of copper compound may be added tothe reaction mixture as metallic copper or as a copper halide. Whateverform of copper compound is employed, it should preferably be added tothe reaction mixture in finely divided form; or, if soluble in theliquid reaction medium, it may be added as a liquid.

Because of the extreme versatility of the present method, the desiredthioether compounds may vary from colorless, mobile liquids to tars ordark, crystalline solids. They may or may not be soluble in the reactionmixture. Skilled chemists, with the present teaching will be able toprepare the thioether products and will be able to separate productsfrom reaction mixture and purify the products by such methods asfiltration, decantation, centrifuging, and in other known methods.

Methods which have been quite broadly useful commonly employ, as a firststep, the removal of the nitrogenous base catalyst material, commonly byreacting it with excess hydrochloric acid in the presence of ice wherebyto avoid producing undesired high temperatures of reaction.Alternatively, the separation from the nitrogenous base has often beensuccessfully carried out by steam distillation whereby components of thedistilled mixture are separated according to their relativevola-tilities; depending upon the nature of the thioether andnitrogenous base, a good separation is usually possible in this methodwhen the temperatures of steam distillation are not injurious. As afurther advantage, this method brings over any substances which formazeotropes with Water vapor.

Another useful technique of which skilled chemists are universally awareis the extraction of product from the neutralized reaction mixture withextractive solvent such as diethyl ether, benzene, dichloromethane,chloroform, or the like.

When it is desired to remove traces of the cuprous catalytic substance,and when distillation or other steps which would effect such removal arenot available or have not succeeded, the mixture may be extracted withstrong aqueous ammonia or with hydrochloric acid. The former formscopper-ammonium complexes which are watersoluble whereas most of thedesired products of the method are not; the latter forms, of course,chlorides which are relatively soluble. Subsequent to such extractions,the product may be recrystallized from solvent.

Little or none of the product substances of the present invention issorbed on activated charcoal. This material, however, tends to sorb andremove numerous impurities. Thus it may be used to decolorize and purifysolvent solutions of the present products.

With the foregoing exemplary procedures, skilled chemists will encounterno undue difficulty in separating I and purifying the products of thepresent method.

The novel thioethers including, particularly, certain of the novelpolymeric thioethers of the present invention, are especially useful tobe employed as lubricants and lubricant adjuvants under particularconditions of extreme pressure and elevated temperature. While the useof sulfur-containing compounds as lubricant additives is old in the art,these compounds have often suffered from the disadvantage of anundesired temperature dependence. In numerous applications to mechanicaldevices of the present day, lubricants must perform Well under severeconditions of pressure, shear, and at temperatures high enough to damagemany lubricant additives. Thermal damage to sulfur-containing lubricantadditives is particularly to be avoided, because some of the pyrolyticor oxidative products resulting from such damage may be compounds whichare relatively reactive with the surfaces, notably metallic surfaces, ofwhich the lubrication one from the other is desired, with the resultthat the breakdown of the lubricant additive greatly accelerates theoccurrence of damage to the surfaces thus lubricated. Under suchconditions, the novel polymeric thioethers have demonstrated unusualvalue.

The following examples illustrate the present invention but are notlimiting as to the scope thereof. This is particularly notable inrespect to the present invention because, of the hundreds ofcombinations of mercaptans and organic halides of which reaction hasbeen attempted, all have succeeded in preparing the desired thioethers.This has been true even when attempting to prepare highly complexthioethers of hitherto unknown structures and very high molecularweights, using starting reactants especially selected as possiblyinoperable. As noted hereinbefore only serious instability or sterichindrance of one or both starting materials, both of which factors canbe ascertained in advance, appear to limit the operability of thepresent invention. Hence, the following examples are illustrative only.

8 EXAMPLE 1 A mixture of 242 grams( 1 mole) Z-S-dibromothiophene, 185grams (2.2 mole) sodium ethylmercaptide, 28.6 grams (0.2 mole) cuprousbromide and 500 milliliters technical 2,4-lutidine was stirred andheated under reflux for 40 hours. The lutidine served both as liquidreaction medium and as nitrogenous base. Upon the completion of the saidheating and stirring, the mixture was poured into flaked ice in 500milliliters concentrated hydrochloric acid. The resulting mixture wasthen extracted with ether, the resulting ether solution removed andwashed once with 10 percent hydrochloric acid and thereafter dried overanhydrous potassium carbonate. The ether solvent was then vaporized andremoved, leaving an oily 2,5-bis(ethylthio)thiophene product which wassubsequently further purified by distillation in vacuum to obtain grams,a yield of 50 percent by weight of starting thiophene or mercaptidecompound, of a colorless liquid boiling at 1l9l21 C. under 3 millimeterspressure.

EXAMPLE 2 EXAMPLE 3 1 ,2,4,5 -tetrakis( ethyl thio) benzene H504 S SCzHs A mixture was prepared consisting of 56.5 grams (0.144 mole) of1,2,4,S-tetrabromobenzene, 60 grams (0.7 mole) of sodiumethylmercaptide, 10 grams (0.07 mole) of cuprous bromide and 280milliliters technical 2,4-lutidine. The resulting mixture was heatedwith stirring under reflux for 44 hours to carry out a reaction andprepare 1,2,4,5-tetrakis(ethylthio)benzene. Upon completion of thereaction, the resulting mixture was then poured into 300 milliliters ofconcentrated hydrochloric acid with which was mixed a generous amount ofice. As a result of this operation a solid separated from the liquidresulting from the melting of the ice in the acid; the said solid wascollected by filtration. The solid was exhaustively extracted withether, the resulting ether solution gently warmed to evaporate andremove ether solvent and obtain 42 grams, 91 percent by weight ofstarting materials, of 1,2,4,5- tetrakis(ethylthio)benzene. The compoundwas further purified by recrystallization from ethanol whereupon itappeared as white crystals melting at 66. 56 8.5 C.

A similar product is obtained from the use of ethyl mercaptan: however,because of its volatility, and because the alkali metal salt gives goodresults, the use of the free mercaptan is not preferred.

EXAMPLE 4 Z-(dodeeylthio) thiazole N i aona l-om A mixture was preparedconsisting of 8 grams cuprous oxide, 22 grams dodecanethiol (dodecylmercaptan), 16.4

grams 2-bromothiazole, 80 milliliters quinoline and 20 milliliterstechnical 2,4-lutidine. The said quinoline-lutidine mixture was employedbecause the pot temperature of the boiling mixture was advantageous incarrying out the present reaction. The resulting mixture was heated withstirring under reflux and under a nitrogen atmosphere, with a waterseparator. The water of reaction of cuprous oxide was thus removed andthe removed quantity noted. After the theoretical amount of water hadseparated, the resulting mixture was stirred and heated under reflux for3 hours. Thereupon, the mixture was cooled to approximately 100 C.whereupon steam was introduced below the surface of the resultingmixture and quinoline and lutidine azeotropically removed. As a resultof these procedures there was obtained a black and tarry residuecontaining a high proportion of the desired 2-(dodecylthio)thiazoleproduct. The said residue was taken up in chloroform, the chloroformsolution filtered, and to the filtrate was added av finely divided,highly activated carbon decolorizing agent. The resulting decolorizedsolution was thereafter again filtered to remove carbon and sorbedimpurities and the resulting filtrate dried over anhydrous potassiumcarbonate. The resulting dried chloroform solution was then gentlywarmed to vaporize and remove solvent and obtain an oily24(dodecylt'hio) thiazole as a crude product. The said crude product wasdistilled and again distilled under subatmospheric pressure to obtain13.8 grams of highly purified yellow oily 2-(dodecylthio)thiazoleproduct boiling at 140 C. under 0.3 millimeter mercury pressure. Theyield was 48.5 percent of theoretical based upon starting materials.

EXAMPLE 5 1,4-bis(dodecylthio)benzene A mixture was prepared consistingof 14.5 grams of cuprous oxide, 41 grams of n-dodecanethiol, 23.6 gramsof p-dibrornobenzene, 120 milliliters 2,4-lutidine and 60 millilitersquinoline. The resulting mixture was blanketed with nitrogen andthereafter heated and stirred to carry forward an initial reaction inthe preparation of desired product. Water of reaction was removed as avapor and caught in a water trap wherein the amount of water removed wasascertained. Upon formation of the theoretical amount of water, theresulting mixture was heated and stirred under reflux for 6 hours. Thehot mixture was then poured into 180 milliliters of concentratedhydrochloric acid containing a relatively large amount of ice. As aresult of these procedures there was formed a brown solid whichprecipitated in the liquid resulting from the melting of the ice in theacid. The said brown solid was allowed to stand for 3 hours andthereafter collected by filtration. The residue from the filtration wasthen taken up in chloroform and filtered. The resulting chloroformsolution was washed twice with 2-normal hydrochloric acid, subsequentlywashed once with water, and thereafter gently warmed in vacuum tovaporize and remove chloroform solvent. As a result of these operationsthere was obtained a light-colored 1,4-bis(dodecylthio)benzene productwhich wa recrystallized twice from ethanol to obtain a relatively purecompound in the form of crystalline white plates melting at 78-79.5 C.The yield following the second recrystallization was 21.9 grams, 45.7percent of theoretical based upon the employed dibromobenzene anddodecanethiol starting materials.

EXAMPLE 6 In manner essentially similar to the foregoing examples, onemolecular proportion of hexabrornobenzene is dispersed in a mixture ofquinoline and pyridine in the presence of a small, catalytic amount(about 5 molecular proportions) of cuprous chloride. To the resultingmixture is added 6 molecular proportions of p-chlorobenzenethiol and theresulting reaction mixture is heated for a period of approximately 3hours at a temperature of about C. The resulting product is dissolved inchloroform and recrystallized therefrom to obtain, in nearlyquantitative yield, a yellow, crystalline hexakis(pchlorophenylthio)benzene corresponding to the structure and melting inthe temperature range of 7l74 C.

Illustrative of the extreme versatility of the present.

method, the hexakis(p-chlorophenylthio)benzene com pound is employed asstarting material in a further preparation wherein it is caused to reactwith either p-tertbutylbenzenethiol or the alkali metal salt thereof,under the conditions stated, to obtain ahexakis[p-(p-tert-butylphenylthio)phenylthio1benzene product as adifiicultly soluble yellow powder.

The compounds of the present invention are useful in various ways. Thoseof greater molecular weight have value as oil additives to improve thelubricity of hightemperature, high-pressure lubricating oils. Those oflow and intermediate molecular weight have value as the active toxicantsin insecticidal preparations; some are herbicidal, and the compounds areof particular value as the intermediate substances to be employed withphosphate substances in the preparation of organic phosphate compoundswhich compounds have been shown to be remarkably effective aspesticides. Various of the compounds prepared according to the presentinvention offer the only practicable intermediate substances en route tonumerous desired organic phosphate compounds and their variousthio-analogues.

I claim:

1. A method for the synthesis of thioethers which comprises causing areaction between a member of the group consisting of a mercaptan and analkali metal salt of a mercaptan, and an organic halide in the presence,simultaneously, of both a nitrogenous base and a source of cuprous ion.

2. Method of claim 1 wherein the reaction is carried out at atemperature in the range of from about 60 C. to about 250 C.

3. Method of claim 1 wherein the nitrogenous base is a solvent liquid.

References Cited by the Examiner UNITED STATES PATENTS 2,685,588 8/54Goshorn et a] 260302 2,744,908 5/56 Young 260302 2,748,145 5/56Muetterlies 260329 2,903,484 9/59 Hardy et al 260609' 2,908,716 10/ 59Cisney et al 260-609 2,922,821 l/ 60 Kundiger et al. 260--609 2,938,9285/ 60 Stevenson et a1 260609 3,068,241 12/62 Sargent 260-329 NICHOLAS S.RIZZO, Primary Examiner.

1. A METHOD FOR THE SYNTHESIS OF THIOETHERS WHICH COMPRISES CAUSING AREACTION BETWEEN A MEMBER OF THE GROUP CONSISTING OF A MERCAPTAN AND ANALKALI METAL SALT OF A MERCAPTAN, AND AN ORGANIC HALIDE IN THE PRESENCE,SIMULTANEOUSLY, OF BOTH A NITROGENOUS BASE AND A SOURCE OF CUPROUS ION.